We do have the option of going with just a cast bullet in either 160 or 180 grain sizes, and it can be put in at 1 k, if we're too concerned with fragile jacketed bullets.
A cast SWC of that weight would almost undoubtedly have enough penetration, but you're going to get little, if any expansion. The thing is, if all you want is to blow a nice clean .45 caliber hole all the way through, a 250gr cast SWC will do it just as well even at the sedate velocity of 700-800fps with moderate recoil and less issue with POA vs. POI in fixed sighted revolvers.
You could, I suppose, use a softer swaged lead SWCHP, but then agian a heavier bullet of the same construction at more moderate velocity such as Federal Champion 225gr LSWCHP already gives us satisfactory penetration and expansion with mild recoil and less issue with POA vs. POI in a fixed sighted revolver so you back to re-inventing the wheel to get something that's already available.
We have the alternative of the 185 bullet at acp velocities of appr 900 to 1k, but if we boosted the velocity, it is a good question whether the original bullet would work. A solid copper would, but a short shanked lead may not. A bonded like a gold dot might. I don't know.
Any bullet, even solid copper or bonded ones, has a velocity limitation. While it's much more difficult to reach, Gold Dots can and have been run too fast. I don't have it handy at the moment, but there's quite a bit of discussion about 180gr .40 caliber Gold Dots overexpanding to the point that the petals wrap back around the base of the bullet when driven at full-power 10mm velocities by Double Tap.
The issue with solid copper bullets like the Barnes XPB is that they are longer, and thus use up more case capacity, than a lead-core bullet of the same weight. This means that they cannot be driven as fast as a lead-core bullet of equal weight unless they are also loaded to higher pressure. A 185gr solid copper bullet at 1200fps might be possible in a Ruger or even a S&W N-Frame, but I wouldn't want to try it in a Taurus 450, Colt SAA, or one of the Italian Colt replicas.
With the specific consideration that a 185 grain bullet meant for 900 fps acp velocities would probably not function well with an extra 200 fps, which I agree, I also have to agree that it would be best to move up to a 200 grain jacketed bullet. with the extra case capacity, you can boost a 200 grain bullet above ACP velocities with an actual reduction in pressures, and by staying with a heavier pistol, remain better off with controllability, I believe, than shooting a 250 grain bullet.
A 200gr JHP in the 1000-1200fps range sounds reasonable as long as you can stay under pressure limits and you use the right kind of bullet. Something like a Hornady XTP would seem like a pretty good choice as they are widely known to work best at high velocity and they don't seem to have a tendency to overexpand or come apart (not to mention that they also have excellent reputations for accuracy). The issue I see here is pressure limits. .45 Long Colt actually has a lower SAAMI max pressure than .45 ACP does due to the large number of older, weaker guns that have been made in .45LC. I suspect that it would be difficult to keep such a loading under SAAMI max pressure, though you could probably advertise it with a disclaimer that its only to be used in certain guns like Buffalo Bore and other boutique makers do.
Any .45 colt load in the 200 grain range will be equal to or better than the .357, IMO, in a lot of criteria.
It depends, I suppose, on what your criteria are. You can probably match or slightly exceed the penetration with similar or slightly more expansion than a full power .357 Magnum with middleweight bullets in the 125-130gr range. However, full-power .357 Magnum loadings in the 158gr or heavier range are probably going to offer a good deal more penetration (such loadings are easily capable of 16" or more penetration in ballistic gelatin).
What I would actually be looking at, after all the discussion, would be a 200 grain appr 1,000 fps round as opposed to the ballpark figure I first used. If a proper bullet could be made, I'd still prefer to go lighter.
That's entirely reasonable as you're basically matching the ballistics of a 200gr .45 ACP +P. If 200gr at 1000fps is what you want, all you'd have to do is select a .451 bullet of the appropriate weight that's been shown to work well in .45 ACP +P loadings (both Speer Gold Dots and Hornady XTP's seem to do well) and load it to the appropriate velocity in .45LC cases. Actually, such a loading already exists in the Cor-Bon 200gr .45 Long Colt +P loading although the Sierra JHP they use might give you some moderate fragmentation.
As it is, any of this stuff would perform better than my 125 grain +P 38s. They would all be the equal of my .357s 158s against man sized targets. having the benefit of big bore can allow one to use heavier, wider bullets without requiring magnum velocities and charges, and should, at least in theory, make a more user friendly round than an intense 1400 fps .357 round.
No doubt it would be superior to almost anything available in .38 Special as the 200gr .45 ACP loadings enjoy a good repuation at the velocities you're describing. The only complaint I ever recall hearing about 200gr .45 ACP JHPs is that some older designs like the Speer "Flying Ashtray" had feeding issues in some semi-autos, but that would obviously be a non-issue in a revolver. I think that such a loading would also compare favorably to 125gr .357 Magnum loadings but, as I said before, I still think that a 158gr .357 Magnum would offer more penetration to those desiring such.
The other drawback to the loading you describe, or any .45 Long Colt loading for that matter, is that a .38 Special or .357 Magnum can be had in a smaller gun or an equal-sized gun with 1-2 rounds greater capacity. That, however, is a compromise that people choosing a .45 LC, .45 ACP, or .44 Spl revolver have obviously considered and are willing to make.
